This invention relates to a tube filling machine and particularly to the holder for frictionally gripping a tube as it is carried through the registration, filling, and crimping stations.
In a tube filling machine, a tube is frictionally placed in a holder with the cap end down and an open end facing upwardly. The tube is filled and thereafter sealed with a crimp across the upper end. The crimp may either be of the folded type used with metal tubes or of the heat sealed type used with plastic tubes. The important aspect of the crimp is that it must be properly oriented with the printed matter on the tube.
The tubes are placed in their holders in the tube filling machine in a random orientation. It is, therefore, necessary to rotate the tube to its correct position before it is filled and crimped so that after crimping the crimp will be properly oriented with respect to the printed matter.
To accomplish the rotation of the tube to the correct position, it is known to frictionally grip the tube in a holder, the holder being placed loosely in a ring carried by the tube filling conveyor. The holder has a central gripper and the tube is pushed into the central gripper.
The tube, thus held, is stopped at a registration station where there is provided a rotator that rises from underneath the holder to engage the holder and rotate it. An electric eye positioned to detect a registration mark on the tube stops the rotator when the electric eye has properly positioned the tube for subsequent filling and crimping.
The registration station places a limitation on the speed of the tube filling machine. Therefore, it is desired to rotate the tube holder as rapidly as possible. This rapid rotation, in turn, requires a good friction grip on the tube, for otherwise the tube, through its inertia, could slip past its correct angular position when the rotator rapidly stops the tube holder.
A tube holder in widespread use bears U.S. Pat. No. 2,574,157. It has multiple parts. It has an outer cylinder and an interchangeable gripper that is secured to the outer cylinder by a snap ring so that it can be replaced by grippers of different dimensions to accommodate tubes of different diameters. The inner gripper is a cylindrical element that has plural windows in its side walls. Plastic gripping jaws are radially slidable in the windows of this cylindrical element. A garter spring surrounds the plastic jaws and urges them radially inwardly to provide the frictional grip on the tube. This complication is required because of the wide variation of the dimensions of tubes of the given nominal diameter. For example, the diameter of a nominally one inch tube may vary as much as 0.035".
The known tube holder thus described is expensive, selling for about $85 a unit. It has one technical problem, namely, that, under some circumstances, it tends to dent metal or laminated tubes when they are crimped. In the crimping process the tube is distorted from a cylindrical shape to an oval shape, and the major dimension of the oval shape pushes against the upper edge of the gripping cylinder putting a dent in the surface of the tube.